Robust B–H perdeuteration of polyhedral boron clusters with D2O by Pd(II)-catalytic electrophilic H/D exchange and intermolecular Pd migration

Abstract

The selective B–H functionalization of carboranes has received considerable attention because of their wide applications in functional materials, catalysis, and pharmaceuticals. Deuterium-labeling experiments and kinetic-isotope-effect experiments are two important tools for mechanistic studies on the selective B–H activation of carboranes. Thus, developing an effective method for the synthesis of perdeuterated carboranes is highly desirable. Herein, we present a practical method for synthesizing perdeuterated carboranes via Pd(II)-catalyzed B–H activation by using D₂O as a deuterium source. This protocol features extraordinary functional-group tolerance, high levels of deuterium incorporation, and ease of scaling. Mechanistic studies illustrate that the deuteration reaction proceeds via Pd(II)-catalytic electrophilic H/D exchange and subsequent intermolecular Pd migration. The same degree of deuterium incorporation across all boron vertices indicates that the Pd-migration step is faster than the electrophilic palladation step. Additionally, the versatility of this method is reflected in the deuteration of other boron clusters.